Building Lightly On the Land

by Amit Armstrong, H. Gabriella Armstrong, and Kenna J. Smith

FHWA's Federal Lands Highway Program creates a safe and effective transportation system for public lands.

The Mike O'Callaghan-Pat Tillman Memorial Bridge, shown
here (top of photo) during construction,
will carry U.S. 93 over the
Colorado River, just south of the
Hoover Dam. The FLHP played a crucial
role in designing the bypass and
corralling the many stakeholders.

From the shifting grounds of southeast Alaskan muskegs to historic Pennsylvania Avenue in Washington, DC, from the volcanic soils of Hawaii to the alpine terrain of the Rocky Mountains, and from the rolling hills of Tennessee to the gulf coast of Texas, building roads in rugged and challenging terrain is the forte of the planners, designers, and engineers of the Federal Lands Highway Program (FLHP).

The Federal Highway Administration's (FHWA) Office of Federal Lands Highway (FLH) is among a handful of Federal agencies that perform highway design and construction management for other Federal agencies. For a quarter century now, the FLHP has essentially served as a consulting engineering firm to Federal land management agencies (FLMAs). Not only does it design roads for difficult terrain, it meets current safety and aesthetic standards while doing so. FLH also has embraced and led the many stakeholders that can be party to expansive or complex projects.

In the Southwest, for instance, Federal, State, and local agencies wanted to build a highway bypassing the Hoover Dam but had to deal with unstable slopes, canyons necessitating switchbacks, and other hurdles. In Washington State, the National Park Service (NPS) needed new guardrails for a road on Mount Rainier but wanted them to blend in with previous construction. In these cases and others, the agencies used FLHP's services to meet their goals.

"The people of FLH are committed to maintain the technical expertise to overcome virtually any engineering challenge and to build enduring partnerships," says Clara Conner, division engineer for the FLHP's Western Federal Lands Highway Division (WFLHD).

Partnerships

FHWA has managed the FLHP since the program's inception 25 years ago, but FHWA's partnerships with other agencies have been key to the program's success. Those partners include the U.S. Department of Agriculture's Forest Service; U.S. Department of Defense (DoD); and the U.S. Department of the Interior's Bureau of Indian Affairs (BIA), U.S. Fish and Wildlife Service (USFWS), and NPS; as well as project-based collaborations with State and local agencies.

"The long-term partnership between FHWA and NPS is an exemplary model of interprofessional and interagency collaboration," says FLH Program Manager Jeff Mann. "By combining teamwork, planning, landscape and engineering design skills, and construction techniques, the partnership embodies what is now called context sensitive design."

Just as each project often involves multiple partners, each also has its own personality. Understanding that character, respecting it, and then building a road in an environmentally sustainable way defines the work of the FLHP and its partners. "While providing and maintaining access to America's treasures is our primary goal, the FLHP provides engineering solutions that meet safety requirements, preserve the natural environment, and satisfy partners' goals," Conner says.

The following seven vignettes capture the spirit of the FLHP and demonstrate the magnitude of some recent projects.

An Island Road in Alaska

On Annette Island in southeastern Alaska, the FLHP played a vital role in jumpstarting a project that had languished since World War II. After founding the Metlakatla Indian Community on the island in 1887, the Tsimshian Indians lived in near isolation from the mainland. A U.S. Coast Guard airstrip began military and commercial passenger transport during World War II, but authorities closed the facility in the 1970s. Sea planes and the State ferry provided transportation to Ketchikan and its hospital and medical facilities after that, but Metlakatla is far from the ferry terminal.

Plans to rectify the situation dated to 1946, when the Alaska Road Commission and U.S. Army Corps of Engineers began planning for construction of Walden Point Road, a 23-kilometer (14-mile) road across the rugged island. The agencies planned to connect Metlakatla, the only federally recognized Indian reservation in Alaska, to the ferry terminal on the northern tip of the island, and thence to Ketchikan.

Despite the commitment made to the Metlakatla community, the project foundered for a half century. In 1997, at the renewed behest of the community, BIA and DoD sought help from the FLHP. The agencies formed a partnership to execute what would become known as Operation Alaskan Road. Under DoD's Innovative Readiness Training (IRT) program, contingents of the Army, Navy, Marine Corps, National Guard, Coast Guard, and Air Force join civil agencies on nonmilitary projects.

"The IRT program is designed to promote civil-military cooperation through projects that use actual work experience to enhance military readiness in addition to helping small communities," says Mike Traffalis, project manager with WFLHD. DoD enlisted the FLHP to apply its roadway design capabilities to Annette Island's rugged terrain and climate. "This project blended the branches of service and civilian workers into a cohesive, productive organization," he says.

In August 2007, Metlakatla held a ribbon-cutting ceremony to inaugurate the two-lane gravel road. The FLHP's challenges had been great. The terrain was mountainous and steep, with heavy vegetation. The climate, which includes average annual rainfall of 381 centimeters (150 inches), limits the construction season to April through October. Compounding matters, the remote location required the team to set up work camps and barge in fuel and equipment and offload it from beach landings along the road.

The Bennett Creek Bridge, shown
here, is one of four bridges constructed
as part of the Walden Point
Road project in Alaska. The bridge
was fabricated in Montana in three
sections to allow for shipping and
remote access construction.

For the final design, the FLHP used drilling and blasting to pass through solid rock cuts and applied subexcavation and backfill to traverse muskeg areas. The road includes four new bridges and four major multiplate arch pipe culverts designed for fish migration using a stream simulation approach.

"WFLHD brought design and construction expertise and partnered with the military, BIA, and Metlakatla community to successfully design and construct this road where no road had been before," Traffalis says.

Skirting Hoover Dam

Since the Hoover Dam was completed in 1936, the two-lane U.S. Highway 93 has crossed the Colorado River on top of the dam. Today, U.S. 93 is the designated CANAMEX Corridor, the North American Free Trade Agreement route between Mexico and Canada. The highway also is a major commercial route among Arizona, Nevada, and Utah, and the primary travel corridor between Phoenix, AZ, and Las Vegas, NV, two of the Nation's fastest growing cities.

U.S. 93 also carries heavy pedestrian traffic to the Hoover Dam National Historic Landmark. The portion of the highway in the vicinity of the dam includes sharp turns, narrow roadways, inadequate shoulders, poor sight distance, and low travel speeds.

Building an improved highway and new Colorado River crossing has been a goal of FHWA, Arizona, Nevada, and the U.S. Bureau of Reclamation for more than 30 years, mostly to accommodate ever-growing traffic volumes. FHWA's Central Federal Lands Highway Division (CFLHD) is responsible for delivering just such a project, and is leading a multiagency management team that also consists of Reclamation, NPS, the Western Area Power Administration, and Arizona and Nevada departments of transportation.

The project has been designated by the U.S. Congress as the Mike O'Callaghan-Pat Tillman Memorial Bridge, honoring two prominent Nevada and Arizona citizens who dedicated their lives to public service and the greater good.

"The Hoover Dam Bypass Project responds to several key needs," says F. David Zanetell, director of project delivery at CFLHD. "It alleviates congestion through a critical trade and commercial corridor, improves safety in an area where the crash rate is three times that of U.S. 93 on either side of the project, and enhances the environment by improving the visitor experience by removing traffic from a national landmark."

But the project posed big engineering challenges. "During development and in close collaboration with the multiagency project management team, we oversaw literally hundreds of the world's best engineering and construction professionals to deliver the facility," says Zanetell.

The team devised a route 457 meters (1,500 feet) downstream of the dam, with 5.6 kilometers (3.5 miles) of new four-lane, divided highway and a 579-meter (1,900-foot)-long bridge that will cross the Black Canyon of the Colorado River and tie into the existing U.S. 93. The new bridge will have the longest concrete arch in North America — 323 meters (1,060 feet) soaring 274 meters (900 feet) above the river. Significant bridge features include precast, posttensioned columns up to 87 meters (285 feet) high, more than 3.2 kilometers (2.0 miles) of rock anchors, 24,466 cubic meters (32,000
cubic yards) of concrete, and 6,632 metric tons (7,310 tons) of structural and reinforcing steel.

"The concrete composite bridge was selected because it offers several advantages over single-solution, cast-in-place bridge construction," says Zanetell. "It allows for an aggressive schedule as progress occurs in parallel onsite during approach structure and arch erection, offsite at the precast yard, and in the shop for fabrication of superstructure steel. In addition, onsite and offsite risks such as weather, labor, and materials availability are mitigated and balanced through the diversified solution."

The multiagency decision to build a composite bridge with steel superstructure and a concrete arch involved a wide circle of engineering professionals and the public. Their consensus was that the composite solution blends the best attributes of concrete and steel.

After settling on the bridge design, the project team next had to actually build the bridge, which is ongoing. The logistics of delivering bridge construction materials out over a steep, rocky canyon is a project in itself. The joint venture team Obayashi USA, LLC and PSM Construction USA, Inc. have drawn on their worldwide experience to develop innovative solutions to many construction challenges. The team is supported by many of the world's foremost long-span engineers and suppliers.

Completion of the bridge requires continuous integration of temporary structures, permanent bridge elements, and construction activities. "The traditional model of roles and responsibilities incorporated on conventional structures simply does not apply," says Zanetell. "Every aspect of the contractors' means and methods must be fully engineered in accordance with preestablished criteria and fully vetted due to the impact on the permanent structure. We have purposefully organized our teams to work collaboratively yet independently to ensure a successful outcome."

Much of the work on the bypass is complete. Finished projects include corridor-wide transmission relocations, approach roadway and structures, and interim surfacing of the approach corridors. All that remains is completion of the bridge centerpiece, already 80 percent finished, and a project to complete the final tie-ins. The bypass remains on the original $240 million budget and is scheduled for completion in the third quarter of 2010.

A commemorative plaque affixed to
this large rock by the Metlakatla Indian
tribe marks the pioneer access road
to the Walden Point Road project.

By developing an alternate crossing of the river near Hoover Dam, the project team is removing car and truck traffic from the top of the dam. More than 17,000 vehicles will travel on the bypass's wider, safer, and less congested U.S. 93 across the Colorado River. Hoover Dam visitors will enjoy improved access and parking, a trail and pedestrian plaza, and a walkway for viewing the majestic dam and Lake Mead. For more information and live images of the project, visit www.hooverdambypass.org.

Back in the Saddle

The U.S. Army constructed Saddle Road during World War II as a one-lane road providing access to military training facilities between Mauna Loa and Mauna Kea on the Big Island of Hawaii. Sixty years later, the FLHP, U.S. Army, Hawaii Department of Transportation, Hawaii County, and other agencies are involved in a major improvement project for Saddle Road.

Saddle Road is the most direct cross-island route for public and commercial traffic between eastern and western Hawaii. However, hazardous conditions limit use of the road — average daily traffic (ADT) is approximately 1,000 vehicles. Deficiencies include substandard road geometrics, poor sight distances, narrow and rough pavement, roadside hazards, lack of shoulders and drainage structures, and minimal signage and pavement markings. Saddle Road has the highest crash rate of any road of its classification in Hawaii.

The Hoover Dam Bypass Project
includes wildlife and canyon crossings
necessitated by the area's environment.

Under CFLHD's guidance, the construction team is adjusting the road alignment to avoid or minimize impacts on Hawaiian cultural values associated with certain types of trees and kipukas (islands of native vegetation within lava flows). The team is implementing pullouts to educate the public about the archeological, historical, and cultural resources and the consequences of abandoning unwanted pets along the roadway, introducing nonnative organisms, and tossing lit cigarettes out of vehicles.

"Construction in this ecologically sensitive area required special contract requirements that are not typical for other road projects," says Eric P. Zeller, project engineer with CFLHD. "The contractor was required to take special precautions in case lava tubes, caves, or native Hawaiian burial or ritual sites were encountered."

In line with the FLHP design, the contractor is clearing trees and shrubs along an irregular edge to create a more gradual transition to remaining vegetation, and blending the cut-and-fill slopes with the surrounding terrain. The contractor replanted the disturbed area with native seeds and plants, and minimized soil exposure to wind erosion during construction.

At the left side of this
photo of the Hoover
Dam Bypass Project,
the south cableway
crane hoists a preassembled
reinforcing
cage for an arch segment
from the bridge
deck of the Arizona
approach and carries it
across the canyon. To
the right, crews construct
the temporary
pylons for the cable
stays on top of a pier.

Contract requirements restrict crews from moving soils with invasive species to other areas. The contractor also needs to steam-clean and fumigate construction equipment before entering the project site, and is subject to restrictions on nighttime lighting to avoid attracting endangered birds and to prevent light pollution at the nearby Mauna Kea observatories.

CFLHD and its partners plan to complete the overall 78-kilometer (48-mile) Saddle Road improvement by 2013, pending availability of funding. On May 29, 2007, the partners held a "maile untying" (the Hawaiian version of a ribbon-cutting) ceremony to commemorate completion of the first 11-kilometer (7-mile)-long segment of the road, the State Route 200 improvement project. Fourteen kilometers (9 miles) more were officially opened to public traffic in December 2008, and CFLHD anticipates opening another 11 kilometers (7 miles) in fall 2009.

Once the overall project is complete, the partners expect the ADT to reach 8,000 vehicles. The improvements also will provide economic and social benefits to the community. The new road will add capacity to the Big Island's road system and reduce congestion on the two other cross-island routes following the northern and southern coastlines. Further, the road will provide an alternative cross-island route during severe weather, natural disasters, or incidents along the coastal routes, and will greatly reduce emergency response times for police, firefighters, and ambulances.

Completing a 200-Year-Old Road

On May 21, 2005, more than 1,000 people attended ceremonies to celebrate the completion of Natchez Trace Parkway in Mississippi. The 715-kilometer (444-mile) parkway commemorates an ancient trail that connected southern portions of the Mississippi River, through Alabama, to salt licks in today's central Tennessee. The Old Natchez Trace was an 805-kilometer (500-mile) footpath that ran through Choctaw and Chickasaw lands connecting Natchez, MS, to Nashville, TN. The Kaintucks, boatmen from the Ohio River Valley, would walk from Natchez to Nashville along the Natchez Trace in about 30 days.

Construction of the new parkway started in the 1930s, but the push to finish the road came in 1998, when the U.S. Congress earmarked $71.5 million for the project. NPS asked FLHP to design and construct the final segments. The curvilinear alignment of the parkway followed the natural topography and minimized excavation and embankment to offer spectacular views of the surrounding landscape and to minimize impacts on the environment.

Because the road itself is the national park that provides access to the historic trace, preserving the viewshed — what visitors can see from the parkway — was important. Natural features such as the soil bluffs of southern Mississippi and limestone outcroppings in central Tennessee offered opportunities for aesthetic design. Crews constructed aggregate-topsoil shoulders to support grass growth and maximize green space along the roadway while providing a stable riding surface.

The FLHP designed the parkway's bridges to emphasize lightness, strength, and ease of construction, and to preserve the viewshed. In fact, the parkway is known for two signature spans, specifically the Tennessee Route 96 double arch bridge and the bridge over Forehand Hollow. The double arch bridge at milepost 438 on the Natchez Trace Parkway was completed in 1994 and received the presidential award for design excellence in 1995 for its innovative design. This bridge is the Nation's first segmentally constructed concrete arch bridge. Spanning 502 meters (1,648 feet), the double arch structure offers motorists a view from 47 meters (155 feet) above the valley floor. The bridge's arches are designed to support the deck without evenly spaced spandrel columns, resulting in a picturesque, unencumbered appearance.

During project construction, the Mississippi Department of Transportation, city of Natchez, NPS, and FLHP worked collaboratively to secure funding and acquire right-of-way. The project used design-build contracting for the first time in Mississippi to meet budget and schedule, and the successful partnership spawned additional collaborative road and bridge projects throughout the State.

A journey through the parkway provides access to a distinct time in the Nation's history. Today, visitors can experience this National Scenic Byway and All-American Road through driving, hiking, biking, horseback riding, and camping.

Accessing Wildlife

In 1999, FHWA and USFWS began a partnership, the Refuge Road Program, to provide maintenance and improvement services for public roads that afford access to or within a unit of the National Wildlife Refuge System. "The expert advice of engineers and designers of the FLHP is integral to the success of the Refuge Road Program," says Sean Furniss, national coordinator of the Refuge Transportation Program at USFWS.

The Natchez Trace Parkway
winds through the
countryside in northern
Mississippi, approaching
the Tennessee River
Bridge. This awardwinning
Scenic Byway
and All-American Road
is a model for context
sensitive design and
reflects a successful long-standing partnership
between FLH and NPS.

In 2002, the Brazoria National Wildlife Refuge (NWR) enlisted the help of CFLHD to pave and widen its 4.8-kilometer (3-mile) entrance road and visitor parking area. Brazoria NWR is located about 48 kilometers (30 miles) southwest of Galveston on the gulf coast of Texas. The refuge receives about 10,000 visitors every year, including almost 300 schoolbus trips. Heavy trucks associated with the oil, gas, and chemical industries also use the road.

The project area is flat with wide, shallow ditches and little to no grades. The original roadway consisted of limestone gravel overlaid atop geotextile fabric. The gravel surface was constructed using locally available limestone aggregate that is soft, breaks up easily, and creates dust. Inadequate design, combined with the gravel surface, caused intermittent flooding of the entrance road during normal rainfall. Heavy rainfall associated with tropical storms could flood the road entirely for a week or more at a time.

Refuge managers decided to upgrade the road to current safety standards by widening and paving it, and improving drainage to create an all-weather driving surface. For the new pavement design, FLHP engineers selected a structural section of 15.2 centimeters (6 inches) of hot mix asphalt pavement over 15.2 centimeters (6 inches) of lime-treated subgrade. During construction, however, the designers quickly discovered that the lime slurry being used was not reacting properly with the subgrade soils and thus was failing to provide the required strength. FLHP tests revealed that the lime was not bonding with the sandy soils brought in from the contractor's source. Testing also showed that dry cement would bond with the sands, and the design parameters could be achieved.

FLHP engineers modified the design to suit the field conditions by using dry cement and increasing the treatment depth to 22.8 centimeters (9 inches). This project marked the first time the FLHP designed and constructed a pavement that could withstand short-term inundation by salty or brackish water. The refuge now features an all-weather road that requires minimal maintenance and a paved, accessible parking area with room for three schoolbuses and 34 cars.

Driving to the Sun

Eivind Scoyen, former superintendent of Glacier National Park, once described the Going-to-the-Sun Road in Montana as "the most beautiful piece of mountain road in the world." The Sun Road, as some abbreviate it, is an 80-kilometer (50-mile), two-lane highway that winds through the heart of the park, up the steep slopes of the Continental Divide, and over the 2,026-meter (6,646-foot) Logan Pass. Motorists can view glacier- carved peaks, deep blue lakes, and lush forests.

The Tennessee Route 96
double arch bridge on
the Natchez Trace Parkway,
completed in 1994,
received a presidential
award for its innovative
design.

The highway itself, built by FHWA's predecessor the Bureau of Public Roads (BPR) from 1921-1937, is designated a Historic Civil Engineering Landmark. BPR built most of the 19-kilometer (12-mile) alpine, or high mountain, section over Logan Pass into the sides of near-vertical cliffs using a network of stonemasonry bridges, tunnels, and arches. A series of 130 retaining walls support the roadbed along the steepest sections, and more than 11 kilometers (7 miles) of guard walls and guardrails help guide motorists and keep them safely on the road. These stonemasonry guard walls give the road much of its historic character and architectural aesthetic appeal.

Today the Sun Road carries more than 475,000 vehicles during Glacier's peak visitor season of June-October, or approximately 3,500 vehicles per day. About 80 percent of the park's 2 million annual visitors travel the road, according to park surveys. However, 70 years of rockslides and avalanches, severe weather, heavy traffic, and inadequate maintenance left the road in urgent need of repair. Without aggressive action, the historic structures for which the Sun Road is so admired might have been lost forever.

In 2003, the FLHP and NPS embarked on a monumental rehabilitation project to modernize the roadway. Already, crews have completed the most urgent repairs on structures in danger of failure. The agencies originally intended to invest $140 million to $170 million over 7 to 8 years to restore the Sun Road's entire length. However, due to lack of funding, complete restoration could take up to 20 years. As a result, both agencies, in partnership with Federal, State, and local officials, are committed to completing the rehabilitation as quickly as funding allows.

The effort involves repairing damaged and deteriorating stonemasonry retaining walls and guard walls, inadequate drainage systems, crumbling pavement, and tunnels and bridges. The FLHP will design safety improvements at high-priority rockfall locations and pullouts, overlooks, and parking areas. A comprehensive mitigation program will limit impacts on tourism. (For more information on the project, see "Virtual Highways — A Vision of the Future" in the May/June 2007 issue of Public Roads, "Saving a National Treasure" in the November/December 2006 issue, and "Living Up to a Landmark" in the March/April 2003 issue.)

Successful planning, design, and construction of this project depend on the longstanding partnership of FHWA and NPS. The partnership is documented in the Telly Award-winning DVD "Path to Partnership: Rehabilitation of the Going-to-the-Sun Road" (FHWA-WFL/TD-08-002).

Preserving an All-American Road

The Beartooth Highway in Montana and Wyoming is a 108-kilometer (67-mile), two-lane highway that crosses some of the most rugged mountains in the lower 48 States. FHWA designated the Beartooth a National Scenic Byway in 1989, and in 2002 named a large portion an All-American Road because of the corridor's historical, cultural, and scenic significance. The highway is an economic lifeline for the Montana resort towns of Cooke City and Red Lodge, and tourists enter Yellowstone National Park through the park's northeastern gate near Cooke City.

Workers are paving the parking lot
at St. Mary Visitor Center at the
east entrance of Glacier National
Park in Montana.

The Beartooth has suffered neglect over the years, partly because it zigzags through three national forests, three counties, and two States. Also, no government agency has claimed ownership of large segments of the roadway through much of its history, earning it the nickname the "orphaned highway."

For rehabilitation purposes, in 1994 FHWA divided the highway into seven segments going west to east, beginning with segment 1 at the park entrance and ending with segment 7 outside Red Lodge. The project steering committee included representatives of FHWA, NPS, the Forest Service, Wyoming Department of Transportation (WYDOT), and Montana Department of Transportation (MDT).

In 1997, WFLHD began designing roadway improvements and faced the challenges of deteriorating pavement, base, and subgrade; inadequate drainage; inconsistent and dangerous roadway geometry; and roadway width that was insufficient to accommodate tour buses and recreational vehicles. The area's hydrology, geology, and climate, combined with high elevations and a short construction season, also posed challenges.

WFLHD designed the new horizontal alignment and vertical profile to maintain the historic curvilinear alignment, for aesthetic reasons, and to improve sight distance and drivability. The agency adjusted the alignment to avoid historical sites such as a cemetery. Because of development near the road, the design included coordinating and purchasing rights-of-way to minimize impacts on businesses, buildings, private parcels, and signs.

Wider shoulders, additional pullouts and parking areas, and improved access have enhanced safety and mobility and improved the driving experience. WFLHD designed those features to maintain community values, ensure visual integrity, and protect travelers and the environmentally sensitive alpine terrain.

The improvements required extensive clearing of trees killed during the Yellowstone fires of 1988. WFLHD designed new drainage structures not for normal hydrology but to account for the great fire; that is, to withstand heavy debris flows such as logs and boulders. The design also called for more than 3.2 kilometers (2 miles) of guardrail to enhance safety and avoid additional environmental impacts. WFLHD designed a weathered steel rail that closely fits the environment and surrounding designs.

Part of the project on
Beartooth Highway
included widening the
turning lanes, shown
here, to Soda Butte
Campground and Daisy
Pass Road. This view from
behind the guardrail near
milepost 4 shows Republic
Peak, a mountain frequented
by backcountry
skiers and snowboarders.

WFLHD, NPS, USFS, MDT, WYDOT, and local businesses teamed up to develop a detailed public information program to update the traveling public on construction activities and any delays or closures. That effort helped minimize construction impacts on traffic. Crews began work on segment 1 in May 2004 and completed it on time and under budget, with no crashes or injured motorists.

The project is an excellent example of how teams can widen, improve, and pave an orphaned highway with minimal impact using a context sensitive approach, according to Greg Gifford, project manager with WFLHD. "The Beartooth Highway, which began as a dirt road to Yellowstone National Park after discovery by trappers and soldiers, stands today as a testament to modern engineering technology and the environmental stewardship vision of the FLHP," he says.

The Mission

FLHP projects exist on remote Alaskan islands and alpine peaks, in desert canyons and in the lush Southeast. No matter the location, the program's more than 600 staff people have a mission to build and maintain the transportation infrastructure that provides safe access to the Nation's natural wonders, ensuring that current and future generations can continue to visit and enjoy them.

Amit Armstrong manages the technology deployment program at WFLHD. He has been with FHWA for 7 years, coordinating deployment of new, innovative, emerging, and underutilized technologies in design and construction of roads on Federal lands projects. He has more than 20 years of experience in numerical simulation and visualization of natural systems. He received his doctorate in civil engineering from Texas Tech University.

H. Gabriella Armstrong is an information technology consultant. When she is not writing in code, she is a freelance writer on food, culture, and travel. She received a bachelor's degree in comparative literature with a minor in Spanish from the University of Colorado.

Kenna J. Smith, of WordSmith Strategies, is a Tucson-based writer who works with public and private clients developing public outreach and education materials, Web site content, and communications strategy.